package tests;

import java.util.Scanner;

public class chouj {
    public static void main(String[] args) {
        long d[] = new long[21];
        d[0]=d[1]=0;
        d[2]=1;
        long f[] = new long[21];
        f[0]=f[1]=1;
        f[2]=2;
        for(int i=3;i<=20;i++){
            d[i]=(i-1)*(d[i-1]+d[i-2]);
            f[i]=i*f[i-1];
        }
        Scanner sc = new Scanner(System.in);
        while(sc.hasNextInt()){
            int n = sc.nextInt();
            System.out.printf("%.2f%%\n",100.0*d[n]/f[n]);
        }
    }
}
